Hi mam
Hope you might have got the following scenario,
1. Tooth might be abraded due to hard brushing, if so go for professional cleaning, application of desensitiser, or filling depending upon the severity and change your tooth brush to soft and paste as sensitive toothpaste.
2. Might be due to caries, please take x ray and proceed with RCT and crown
Next Steps
Visit the dentist for investigation
Health Tips
Don't use hot water gargle, it will increase your pain.
As of now take pain killers ( dolonex dt), if you don't have any health issues and report to dentist tomorrow it self.
Hope this helps you mam